When describing the length of the yugasor ages,
and which yugawe are in and how far along we are in it, there is
sometimes confusion about how to calculate them. A number of theories have
cropped over the years regarding how the yugastranspire. The problem is
when they are figured only according to years of earth’s time, they will never
be accurate. They are described in the Vedic literature according to the
celestial years, or years of the Devas. Nonetheless, there are specific
references in the Vedic texts which make it clear how to calculate them. For
starters, the Mahabharata (Shanti Parva, 231.12-20) explains it in
detail:

"The rishis, measuring time, have given particular names to particular
portions [of time]. Five and ten winks of the eye make what is called a Kastha.
Thirty Kasthas make what is called a Kala. Thirty Kalas, with the tenth part of
a Kala, make a Muhurta. Thirty Muhurtas make one day and night. Thirty days and
nights form a month, and twelve months form a year. Persons well-read in
mathematical science say that a year is made up of two solar motions, meaning
the northern and southern. The sun makes the day and night for men. The night is
for the sleep of all living creatures, and the day is for work. A month of human
beings is equal to a day and night of the departed manes [ancestors who have
gone on to the subtle worlds]. That division consists in this: the light half of
the month is their day which is for work; and the dark fortnight is their night
for sleep. A year (of men) is equal to a day and night to the gods [Devas or
celestials]. This division consists in this: the half year for which the sun
travels from the vernal to the autumnal equinox is the day of the gods, and the
half year for which the sun moves from the latter to the former is their night.
[Thus, an earth year is but a day for the Devas.] Calculating by the days and
nights of human beings about which I have told you, I shall speak of the day and
night of Brahma and his years also. I shall, in their order, tell you the number
of years, that are for different purposes calculated differently, in the Krita,
the Treta, the Dvapara, and the Kali yugas. Four thousand celestial years is the
duration of the first or Krita age. The morning of that cycle consists of four
hundred years and its evening is of four hundred years. [Note: This says
celestial years, or years of the demigods on the higher planets. Such years are
much longer than those of planet earth. So 4000 celestial years, with the
morning or Sandhya of 400 celestial years and the evening or Sandhyansa, or
intermediate period, of another 400 years equals 4800 celestial years or
1,728,000 human years.]

"Regarding the other cycles [or yugas], the duration of each gradually
decreases by a quarter in respect of both the principal period with the minor
portion and the conjoining portion itself. These periods always keep up the
never-ending and eternal worlds. They who know Brahma, O child, regard this as
Immutable Brahma." (Mb, Shanti Parva, 231.21-22)

This means that as each age or yuga appears, from the Krita, Treta,
Dvapara, to Kali, each yuga decreases by a quarter of the previous
yuga, in addition to the conjoining Sandhya and Sandhyansa periods with each
yuga. In this way, it is roughly calculated that a whole cycle of the
four yugas, namely Krita, Treta, Dvapara, and Kali-yuga together, total about
12,000 celestial years in length.

The Mahabharata (Shanti Parva, 231.29-32) continues: "The learned say
that these 12,000 celestial years form what is called a cycle. A thousand such
cycles form a single day of Brahma. The same is the duration of Brahma’s night.
With the beginning of Brahma’s day the universal entities come into being.
During the period of universal dissolution the Creator [Brahma] sleeps in
Yoga-meditation. When the period of sleep expires, He awakes. What is Brahma’s
day covers a thousand such cycles. His night also covers a thousand similar
cycles. They who know this are said to know the day and the night. On the expiry
of His night, Brahma, waking up, modifies the indestructible intelligence by
causing it to be overlaid with ignorance. He then causes Consciousness to spring
up, whence it originates Mind which is at one with the Manifest." [This creative
process is described in detail in my book How the Universe was Created and
Our Purpose In It.]

In calculating the duration of the different yugas, there are a few
differences between the Puranas, otherwise their descriptions are all the
same. The Brahmanda Purana (1.2.29.31-34) specifically states that Krita
or Satya-yuga is 1,440,000 human years in length, Treta-yuga is 1,080,000 years,
Dvapara-yuga is 720,000 years, and Kali-yuga is 360,000 years in length. The
Linga Purana (4.24-35) also agrees with this except for Treta-yuga, which it
says is 1,800,000 years in length. These figures are correct when we leave out
the conjoining Sandhya [at the beginning of each yuga] and the Sandhyansa
[ending of each yuga] periods.

When explaining the various measurements of time, the Vishnu Purana
(Book One, Chapter Three) and the Srimad-Bhagavatam (3.11.19), along with
the Bhagavad-gita (8.17), the Vayu Purana (Chapter 57), and
Bhavishya Purana (Brahma Parva, 2.86-107), and others, such as the
Mahabharata as quoted above, also all agree on the measurements of the
durations of the yugas. This shows that these time measurements are corroborated
throughout the Vedic texts, and if anyone has a different theory about the Vedic
time frame, then they are going outside the Vedic descriptions. We will describe
this in more simplified terms as follows:

In the explanations of the measurements of time found therein, one cycle of
the four yugastogether is 12,000 years of the demigods, called divine
years. Each of these years is composed of 360 days, and each of their days is
equal to one human year. So Krita-yuga is 4000 divine years in length,
Treta-yuga is 3000 divine years in length, Dvapara-yuga is 2000 divine years in
length, and Kali-yuga is 1000 divine years long, each one a quarter less than
Krita or Satya-yuga, with the addition of the conjoining portions of the Sandhya
and Sandhyansa.

In this way, each yuga is preceded by a period called a Sandhya, which
is as many hundred years in length as there are thousands of years in that
particular yuga. Each yuga is also followed by a period of time
known as a Sandhyansa, which is also as many hundreds of years in length as
there are thousands of years in the yuga. In between these periods of
time is the actual yuga. Therefore, we have:

This equals 4,320,000 human years, or 12,000 divine years, in one cycle of
the four yugastogether, and 1000 cycles of these yugasequals a
Chaturyuga at 12,000,000 divine years and 4,320,000,000 human years in
one day of Brahma. It is also explained that Kali-yuga began with the
disappearance of Lord Krishna from the planet. This has been calculated to be
3102 BCE. Since Kali-yuga is described as being 432,000 earth years in length,
with 5,000 years and more already passed, then the age of Kali-yuga has
approximately 326,000 more years to go.

To be more clear about this, these calculations are further confirmed in the
Brahma-Vaivarta Purana which relates the same figures in the following
way:

"Now I will tell you about the counting of time. As the days rise and end,
similarly all the four yugasalso come and end. A single divine day and
night of Manu compares with the completed year of the humans. Those well-versed
in the signs of time, ordain that after the passing of the three hundred and
sixty yugasof the humans, a divine yuga of the gods is made.
Seventy-one divine years [of the gods] comprise a manvantara. An age of
Indra is equivalent to one manvantara. Thus, after the existence of
twenty-eight Indras, there is one day and night of Brahma. Thus, after the lapse
of one hundred and eight years, the life of Brahma comes to an end." (Brahma-Vaivarta
Purana, Prakriti Khanda, 7.72-75)

The same time frame is calculated with a different description in the
Kalki Purana (19.12-14) as follows:

"Twelve thousand years of the demigods is the duration of the four yugason earth. The duration of Satya-yuga is four thousand celestial years,
Treta-yuga is three thousand celestial years, Dvapara-yuga is two thousand
celestial years, and Kali-yuga is one thousand celestial years. The transitional
periods of the four yugasare four hundred, three hundred, two hundred,
and one hundred celestial years respectively. In this way, the total comes to
twelve thousand celestial years. The duration of the reign of each Manu is
seventy-one cycles of the four yugas. Fourteen Manus reign during one day of
Brahma. This is also the duration of Brahma’s night [which is as long as his
day]."

To understand this in greater detail and to also show the consistency of
these calculations throughout the Vedic literature, we can use the additional
example. Here Suta Gosvami explains to the sages during the huge gathering at
the forest of Naimisaranya 5000 years ago, all of the divisions of time and how
the lengths of the yugasare formulated, as related in the Vayu Purana.

"In the context of the description of the earth, etc., I have already said
about the four yugas. Now I shall recount them in detail. (Listen and)
understand them. Calculating everything and mentioning in detail, I shall
narrate in full the six aspects of yugas, namely yugabheda (difference in
yugas), yugadharma (the particular characteristics of each yuga),
yugasandhi (the junction of yugas), yugamsha (the parts of yugas),
and yugasandhana (the joints of the yugas). The human year can be
understood (calculated) by means of valid working knowledge. Calculating on the
basis of that year [in the human time frame], I shall explain the four yugas.
The time taken to utter a short syllable is equal to a Nimesha. Nimesha, Kashtha,
Kala, and Muhurta are the units of time. Fifteen Nimeshas constitute a Kashtha,
thirty Kashthas make one Kala, and thirty Kalas make one Muhurta. Thirty
Muhurtas make one full day and night. The sun demarcates the human as well as
the divine days and nights. The day is intended for activity and the night is
meant for sleep. A (human) month constitutes the day and night of the Pitris
[the departed ancestors, now included as part of the celestials]. Its division
is thus: The dark half is the day for them and the bright half is their night
for sleep [as calculated by the waning and waxing of the moon]." (Vayu Purana
57.2-9)

"Therefore, thirty human months make one month of the Pitris [the celestial
ancestors]. On the basis of the human calculation, three hundred and sixty
months constitute a year of the Pitris. A hundred human years constitute three
years and four months of the Pitris. A human year in accordance with the human
calculation is one day and one night of the Devas [the higher demigods]. This is
the conclusion in this scripture." (Vayu Purana 57.10-12)

"So, the divine day and night together [of the Devas] make a human year. A
further classification is that the Uttarayana period (northern transit of the
sun) is the day and the Dakshinayana period (southern transit of the sun) is the
night (of the Devas). Thirty of the days and nights of the gods, or thirty human
years make one divine month (of the gods). One hundred human years make three
divine months and three divine days. Thus is the divine reckoning for divisions
of time." (Vayu Purana 57.13-15)

"Three hundred and sixty years according to human calculation constitute one
divine year. Three thousand and thirty years according to human calculation
constitute one year of the Seven Sages (Saptarishis) or the (astrological
constellation of) the Great Bear. Nine thousand and ninety human years make one
Kraunchan year. Thirty-six thousand human years should be known as one hundred
divine years. Thus is the calculation of the divine unit of time. Persons well
versed in calculation say that three hundred and sixty thousand (360,000) years
reckoned on the basis of human time units constitute a thousand divine years [of
the Devas]. It is thus that the sages sang about the divine calculation. They
have formulated the reckoning of the yugasand their duration on the
basis of this divine calculation." (Vayu Purana 57.16-21)

Now with all of this calculating we reach the point where it is used to
establish the durations of the four yugasas followed:

"Wise people know that there are four yugas in Bharata Varsha [the area of
India and sometimes considered planet earth in general]. The first one is Krita,
followed by Treta, Dvapara, and Kali-yuga. One should reckon these yugas in this
order. They say that the Krita-yuga consists of four thousand years. The Sandhya
(transition period) consists of as many hundreds of years (400 divine years).
The Sandhyamsha (part of the junction with the next yuga) is equal to the
Sandhya period. In the Sandhyas and Sandhyamshas of the other yugas there is a
gradual reduction of a thousand [years of the yuga] and hundred years [in the
Sandhya and Sandhyamsha transitions]. [This means that] Treta-yuga contains
three thousand years, and its Sandhya and Sandhyamsha [junctions with the
preceding and following yugas] consist of three hundred years each. The wise say
that Dvapara-yuga contains two thousand [celestial] years, and the Sandhya
consists of two hundred years and the Sandhyamsha is equal to the Sandhya [two
hundred years]. The learned say that Kali-yuga consists of a thousand years, and
its Sandhya is of a hundred years and the Sandhyamsha is the same. This period
of twelve thousand (divine) years is known as a Maha-yuga. The four yugas
together are Krita, Treta, Dvapara, and Kali." (Vayu Purana 57.22-28)

"In this world the calculation of years is based on the human level. Now I
shall mention the duration of Krita-yuga in accordance with that type of [human]
calculation. The duration [of Krita-yuga] is one million, four hundred and forty
thousand [human] years. As for Kali-yuga, it is one fourth of that. Thus the
specific duration of time of the four yugas excluding the Sandhyas and
Sandhyamshas is declared. Including the Sandhyas and Sandhyamshas the duration
of the four yugas put together is four million three hundred and twenty thousand
[4,320,000] human years." (Vayu Purana 57.29-32)

Thus, we have provided the different ways of explaining the units of time to
calculate the length of the yugas according to the references in the Vedic
texts. I hope this has provided enough information and evidence to clarify and
conclude what is sometimes a confusing issue, and that the same figures and
conclusions are arrived at in various texts.

THE MANU AVATARAS

To more clearly understand the division of time known as a

manvantara, or the life span of one Manu, the full
explanation is provided herein. First of all, the Manus appear for certain
durations within a day of Brahma. Brahma’s day is calculated as 4,300,000 years
(the time of one cycle of the four yugas) times 1,000, or about 4,320,000,000
human years. Within one day of Brahma there are 14 Manus. The list of the 14
Manus in this universe is as follows: Yajna is Svayambhuva Manu, Vibhu is
Svarocisha Manu, Satyasena is Uttama Manu, Hari is Tamasa Manu, Vaikuntha is
Raivata Manu, Ajita is Ckakshusha Manu, Vamana is Vaivasvata Manu (the Manu of
the present age), Sarvabhauma is Savarni Manu, Rishabha is Daksha-savarni Manu,
Vishvaksena is Brahma-savarni Manu, Dharmasetu is Dharma-savarni Manu, Sudhama
is Rudra-savarni Manu, Yogesvara is Deva-savarni Manu, and Brihadbhanu is
Indra-savarni Manu. These fourteen Manus cover the 4,320,000,000 solar years of
one day of Brahma. (Srimad-Bhagavatam 1.3.5 purport &
Chaitanya-caritamrita, Madhya-lila 20, 319-328)

To understand more completely how long these Manus reign we can consider the
following information. For example, there are four ages, namely Satya-yuga,
Treta-yuga, Dvapara-yuga, and Kali-yuga, which together comprise a divya-yuga,
which is one set of the four yugas, also called a chatur-yuga. Let us remember
that Satya-yuga lasts 1,728,000 years, Treta-yuga 1,296,000 years, Dvapara-yuga
864,000 years, and Kali-yuga 432,000 years. That is a total of 4,320,000 years.
A day of Brahma, called a kalpa, lasts for 1,000 of these cycles, and is
thus 4,320,000,000 solar years. There are 14 Manus in each day of Brahma. Each
Manu is said to exist for one manvantara, which is a period of time
lasting 71 divya-yugas. Therefore, each Manu exists for roughly 306,720,000
years. Additionally, Brahma lives for 100 years, composed of 365 of such days in
a year. (Bhagavad-gita 8.17 & Srimad-Bhagavatam.3.11.20 &
Vishnu Purana, Book One, Chapter Three, p.35)

From further analysis we can also discover the age of the earth from these
Vedic calculations. The present Manu is the seventh in line, called Vaivasvata
Manu, the son of Vivasvan. Twenty-seven divya-yugas, or cycles of the four yugas,
of his age have now passed. So 27 divya-yugas means 116,640,000 years. It is
scheduled that at the end of the Dvapara-yuga of the twenty-eighth divya-yuga of
the seventh Manu, Lord Krishna appears on earth with the full paraphernalia of
His eternal spiritual abode, named Vrajadhama or Goloka Vrindavana. Brahma’s day
consists of 4,320,000,000 years. In this way, six of these Manus appear and
disappear before Lord Krishna takes birth. This means that 1,975,320,000 years
of the day of Brahma have gone by before the appearance of Lord Krishna. (Chaitanya-caritamrita,
Adi-lila 3, 7-10 & Srimad-Bhagavatam 4.30.49 purport)

Therefore, this is also the age of the earth in this particular day of Brahma
by these Vedic calculations. Science is sometimes surprised that such lengths of
time were part of the ancient Vedic conception of the universe.